The present invention relates to wireless communication, and more specifically, to an adaptive modulation coding method and an apparatus thereof.
In a wireless communication system, Adaptive Modulation Coding (AMC) is widely used in order to enhance throughput of the whole system. AMC is a technology which adaptively changes modulation and coding scheme according to channel condition. Its basic working principle is as follows: a user at center of a cell, due to has better signal-to-interference-plus-noise ratio (SINR), is usually assigned a higher modulation coding scheme or coding rate to enhance throughput, e.g., 64QAM, Turbo code with 3/4 code rate; whereas a user at edge of a cell, whose SINR is low, is assigned lower modulation or coding rate (e.g., QPSK, Turbo code with 1/2 code rate) in order to ensure stability of the user. Using AMC has the following advantages: (1) user in a better channel condition can be assigned higher modulation scheme and coding rate, which can enhance average data throughput of the whole cell; (2) link level AMC that changes based on modulation coding scheme can reduce change in interference, as compared to the method that controls transmission power; and (3) by combining AMC with time domain scheduling, user terminal is maintained in a low fading status by utilizing fast fading feature of the terminal.
A typical process for downlink AMC is as follows: user terminal estimates SINR of the downlink in real time, and reports the estimated SINR information to a base station, the base station will determine a downlink modulation coding scheme to be used by user according to the SINR information reported by the user terminal. Such a working mechanism is widely used at present. If current system environment is ideal and there is no interference during data transmission, then such a mechanism may obtain relatively good performance. However, when there is interference in system's working environment, SINR estimated by the user terminal may not be able to truly reflect status of the wireless channel, resulting in that the modulation coding scheme determined according to this parameter is not the most appropriate. If modulation coding scheme of the user terminal is set too high, it will cause a large number of error codes, making system operation unstable. If modulation coding scheme of the user terminal is set too low, throughput of the system will be wasted.
Thus, there is a need for a method that can flexibly adjust modulation coding scheme employed by a user terminal in an interference environment.